FortiSwitches connected direct to FortiGate instead of L3 Cisco switch?

I was given four FortiSwitch 148Fs, but don't have enough ports on my L3 Cisco switch to plug them into.

My LAN routes are known to the FortiGate via OSPF

If I plug my FortiSwitches directly into the FortiGate, will they learn the subnets from the core? Or would this be considered a bad topology?